1. Field of the Invention
The present invention concerns an x-ray radiator to generate quasi-monochromatic x-ray radiation, and a medical radiography x-ray acquisition system embodying such an x-ray
2. Description of the Prior Art
X-ray systems for x-ray-based medical imaging are known with the following design. A point-shaped x-ray source (bremsstrahlung generated by an x-ray beam at an anode) in an x-ray radiator emits polychromatic x-ray radiation. The radiation can be brought into the shape of a delimited fan by a collimator. The x-ray radiation penetrates a subject to be exposed, in which the radiation is attenuated before it is received by an image receiver with spatial resolution. In the use of such x-ray systems, a significant efficiency loss occurs due to the polychromatic braking spectrum. It is known that for each task, i.e. the imaging of a specific subject within a defined background and a given geometry—there is precisely one quantum energy that represents the optimal compromise between patient dose, contrast and noise, and therefore has the highest efficiency. A polychromatic spectrum therefore inevitably contains spectrum portions that are superfluous or disruptive for the task at hand. Since energies adjacent to the optimal quantum energy likewise have a very high efficiency, to satisfy the object of a good image quality it is sufficient to use a somewhat more broadly spread quantum energy (quasi-monochromatic), for example limited to a range of approximately 15 keV. In comparison, a perfectly monochromatic x-ray radiation insignificantly increases the efficiency.
A tunable, quasi-monochromatic, efficient x-ray radiator is a requirement for an ideal x-ray system, however, the production of a quasi-monochromatic x-ray beam from the polychromatic spectrum is complicated. A common method to achieve this approximately is the diffraction of the polychromatic x-ray radiation (generated with the use of known x-ray sources) by the Bragg diffractions (see FIG. 2) at crystals. However, such methods always contain a very large radiation intensity loss both spectrally and spatially. For this reason such x-ray radiators according to the prior art have generally not been used in the radioscopy of large and thick tissue slices, or only what are known as scan exposures are implemented.